89″. 3-1/2″ stock bore x 4-5/8″ stroke. Used with stock cylinders and heads in combination with 4-5/8″ stroker flywheels. Converts the stock 80″ (1340cc) Evo B.T. to 89″ (1459cc). Approx. 9.25:1 CR. Kits include forged pistons, wrist pins, wrist pin clips and piston rings. Note: In any and all applications the technician must be able to judge components for their suitability in combination with the other engine components, prior to installation. It is of importance that a knowledgeable mechanic will install & make adjustments as required. The rider must follow standard break-in and riding procedures for overhauled engines.